FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for processing an object to be processed in a vacuum container under a reduced pressure therein by using a processing liquid and also to a method of manufacturing a dry food by processing a material in a reduced-pressure vacuum container and by removing oil from and drying the processed material.
The present invention, though most suited for the manufacture of a dry food, also has a wide range of applications, including the one of heating and drying wastes such as kitchen garbage to form compost.
Commonly used dry food making methods include a vacuum frying method. For example, Japanese Patent Application Publication No. 28865/1977 discloses an apparatus for making confectionery-like foods which has a frying area and a cooling area in a vacuum tank, and which fries a food material in the frying area and cools and hardens the fried material on a cooling table in the cooling area.
Other apparatuses, disclosed in Japanese Patent Application Laid-Open Nos. 183048/1983 and 92718/1985, place the material in contact with heated oil under a reduced pressure and remove the oil from the material under a reduced pressure to make dry foods continuously. A continuous vacuum fryer apparatus, disclosed in Japanese Patent Application Publication No. 59230/1995, seals the vacuum container from the outside by operating rotary valves installed in a liquid container and a transport passage, carries the food material into the vacuum container, and continuously heats the material with oil at a predetermined temperature in the vacuum container.
In the above-mentioned conventional apparatuses, the vacuum frying apparatus described in Japanese Patent Application Publication No. 28865/1977 is an apparatus for making a raised food which fries the material in the frying area and hardens the fried material in the cooling area while maintaining the raised state of the fried material. In this apparatus, because the fried material which is carried in the cooling area raises and hardens with the oil soaked in the fried material, it is not only impossible to remove the excessive oil in the food but also to obtain a good dry food which maintains an ideal porous state with the minimum oil soaked.
Because both the dry food making apparatuses described in Japanese Patent Application Laid-Open Nos. 183048/1983 and 92718/1985 directly expose the material to heated oil under a negative pressure thereafter removing the oil from and drying the material, the rapid change in the pressure and the high temperature of the oil cause rapid evaporation to the surface of the material, make it impossible to maintain an ideal porous state, and degrade the quality as a dry food. An infrared generator and a microwave generator, though their use may be effective, are expensive and, considering the service lives of the microwave generator and the cyclotron, they are not practical.
As for the continuous vacuum fryer apparatus disclosed in Japanese Patent Application Publication No. 59230/1995, the speed governing between the transport chain to which the processing container accommodating the material to be processed is secured and the rotary valves installed in the liquid container and the transport passage is complicated, rendering the high productivity not expectable. This prior art does not mention to the oil removing operation under a negative pressure, which is most effective in removing oil soaked in the material. Because the material is brought into contact with the oil at once, the quality as the dry food is degraded. Furthermore, because a plurality of oil tanks are arranged in series, the liquid container is elongate increasing the size of the apparatus as a whole.